Tl;dr: Pen is 10/10. Nib and writing experience is a boringly smooth, semi-stub nail. Unless seeking a No.8 Nail of a Nib, or seeking a pen to hold a different No.8 Nib, it's nearly impossible to recommend over the Kakari.
The Fifty4T Titan is a special pen. In this forged carbon fibre variant, it is light weight, it carries a good, but not overwhelming amount of ink, it is comfortable in the hand. The carbon is textured, but not unpleasant. This is a 10/10 pen from its build quality alone.
I am an owner of a Kyuseido Kakari as well as this pen, and the comparison cannot be ignored. Size wise, while some YouTube reviews claim they are bigger, sitting them next to each other shows that outside the physical nib itself, and the section thickness, the pens are roughly the same size. Rumor and general workmanship suggests than either Ben Walsh offered some consultation on the Fifty4T Titan or that it is manufactured in the same facility. The high quality that exudes from the pen as a result is unsurprising.
Subjectively, it is the writing experience where this falls apart for me. I inked it up and began using it, and it wrote perfectly... fine. There is nothing special about the writing experience if you own a similarly-built pen already. The feel in the hand, the way it handles as you write... these are familiar, and in a good way. But the nib is not special like other pens in its class. It's smooth, it works, the ebonite feed provides good flow (and is a huge plus here), but the nib itself, the thing that contacts the page and connects you to the ink is lacking. And it stands out. It doesn't help how the laser-etched logo also strikes a non-cohesive tone to an otherwise lovely industrial design. Out of interest, I compared the nib to that in the Gravitas Monster and also the Moonman/Majohn P140, and found that the profiles of all these nibs are the same. They write the same.
Another disappointment is how little this pen can be deconstructed for maintenance. The section is glued. The rear assembly requires specialised equipment. You can remove the nib, but this voids the warranty (this is no different than the Kakari, or a Pilot 823, mind you). It provides the impression that the manufacturer does not believe their pen will survive heavy-handed maintenance. Not a good look in this price class either. Especially without a roll stop of any variety. All this being said, I knew this before purchasing, and am ok with these restrictions for the most part.
This pen is, with VAT, around 850 Euros. A Kakari runs about 100 Euro less. I am not asking for a gold nib here. I'm not asking for anything fancy. I am asking for something that feels different. I find it difficult to believe that a soft steel nib cannot be developed or sourced, or that the market for this pen would have been so shrunken by offering a Titanium Nib for a 100 Euro surcharge. At the very least, I cannot believe a pen in this price class is using a nib with laser-etching instead of at least stamping. Something, anything, to make it feel or look as special and different as the pen itself.
I don't regret this purchase at all. I bought it explicitly knowing that the nib was likely to be unimpressive, which would make the justification of putting a King of Pen nib in it much easier. But this is out of reach for many, as the King of Pen, especially in Europe, MSRP's for way over what it should.
If you read this far, I hope it helps.